Barium c20-c22 soap-barium carbonate grease composition and process for forming same



more fully appear.

3,010,898 BARIUM C -C SOAP-B CONATE GREASE CQMPOSITION PROCESS FOR FOG SJohn W. Wiison, .lr., Redding Ridge, 'Conn., assignor to Socony MobilOil Company, Inc, a corporation of New York No Drawing. Filed May 20,1959, Ser. No. 814,400 10 Claims. (Cl. 252-18) The present inventionrelates to lubricating greases especially adapted for use under a widerange of operating temperatures and under unusually high bearing loads.More particularly, it relates to such lubricating greases consistingessentially of a petroleum lubricating oil fraction thickened to thedesired grease consistency by incorporating therein a thickening orgelling agent comprising a barium soap of a long chain fatty acidproduced in situ by reacting the fatty acid, while admixed with the oilfraction, with a substantial excess of colloidal barium carbonate, theexcess barium carbonate remaining in the finished grease as reserve baseserving to neutralize acidic materials with which it may come in contactduring use and, apparently, also serving other useful functions.

The invention provides improved greases of the type described and alsoprovides an improved method for the manufacture of such greases.

Lubricating greases have, for decades, been produced by thickeningpetroleum lubricating oil fractions with a soda or lime soap of oleic,palmitic or stearic acid, or mixtures thereof, by saponifying the fattyacid in admixture with the mineral oil. Soaps of other metals have alsobeen used in the manufacture of lubricating greases.

It has also been proposed to effect the thickening of lubricating oil bydispersing therein inorganic colloids in expanded form, such as gels orclays, or certain unneutralized oxides or carbonates, carbon black orthe like. More recently, it has been proposed to produce lubricatinggreases by thickening an oil lubricant with colloidal calcium carbonatewhich has been coated, or in some way complexed by chemical interaction,with a calcium salt of a low molecular weight dibasic aliphatic acid.

To my knowledge, none of the greases so produced have been entirelysatisfactory for lubricating parts subject to high temperature operatingconditions under extremely high bearing loads. invention, and myimproved method of producing such greases, are distinguished from thegreases and procedures of the prior art in several important respects aswill hereinafter appear.

It is an object of my present invention to produce lubricating greasescontaining reserve alkalinity and which are stable against separation instorage and against separation or leakage of oil under high temperatureoperating conditions and which are capable of maintaining efiiciencylubrication under unusually high bearing loads.

It is a more specific object of the invention to produce such greaseshaving A.S.T.M. dropping points of at least 300 F., and preferably inexcess of 350 R, which under the A.S.T.M. wheel bearing performance testat 220 F. suffers an oil leakage not exceeding about 10 grams, andpreferably less than grams, which by the rolling stability. test at roomtemperature will show a final micro penetration not exceeding 230, andwhich passes the four-ball weld test at a load of 200 kgs. These objectsare attained by my present invention, aswill hereinafter As indicatedabove, the process of thelpresent inven- .tion, broadly stated,comprises the reacting of a fatty acid, while admixed with a petroleumlubricating oil The greases of my present I fraction, with a substantialexcess of colloidal barium operation as just broadly stated will notresult in a lubricating grease meeting the above-noted specifications,unless several important conditions, hereinafter described, are met. Y

I have found that for producing such greases having these desiredproperties, the characteristics of the colloidal barium carbonate usedare of utmost importance. While I cannot describe with certainty theessential characteristics of the carbonate, there has been developed anovel process by which colloidal suspensions of barium carbonate inmethanol, having the characteristics essential for my present purpose,may be consistently produced, and which is the subject matter ofcopending application Ser. No. 814,399, filed concurrently herewith. Itis my present belief that the unique qualities of the resultant colloidare in some way related to the particle diameter or structure or surfacechemistry of the colloidal particles or some combination of thoseproperties, not fully understood. The particle diameters of suchsuspensions, which I have used with particular advantage, have beenshown by electron microscope examination to be rela-- tively uniform andto fall within the range of 0.02 to 0.2 micron.

According to the process described and claimed in the above-notedcopending application, barium oxide in pro-- portions within the rangeequivalent to about 10% to about 15% barium, preferably about 12.5%, isreacted with anhydrous methyl alcohol to produce a clear solution. Thenan amount of water within the range of about 1 mol to about 4 mols,preferably about 2 mols, per mol of barium present in the solution, isadded to and thoroughly dispersed in the solution to form a homogeneousmixture. The solution is then carbonated by dissolving carbon dioxidetherein in a molar proportion at least equal to the mols of bariumpresent therein. The foregoing steps may be carried out at ambienttemperatures and pressures. The resultant mixture is then mildly heatedto a temperature of about 153 F. with refluxing for a period ofapproximately one-quarter hour, until a substantially clear colloidalsolution of the carbonate is obtained.

This preformed colloidal suspension of the barium carbonate in methanolis, in accordance with my present invention, mixed in suitableproportions with the petroleum oil fraction and the fatty acid and themixture heated to evaporate the alcohol, promote reaction of thecarbonate with the fatty acid and drive off the water.

A further important condition which must be met in carrying out myprocess is the rate at which the methanol is expelled from this mixture.Upon evaporation of the methanol, the mixture assumes a semi-fluidconsistency. I have found, however, that if the methanol is expelled toorapidly, a grease satisfactory for my present purpose will not result.It is my present belief that this is due to some change in the characterof the colloid brought about by too rapid expelling of the methanol. 7

In laboratory size batches, I have found that the desired results areobtained where at least the major portion of the methanol is driven oifby gradually heating the mixture, without mechanical agitation, to amoderate temperature, of the order of -200 F., for a period ofabout onehour. The optimum temperature and extent of this preliminary heatingstep will vary somewhat with the volumeof the batch and the dimensionsof the heating vessel Asa general guide in this respect, I have foundthat the rateof expelling the methanol should not exceed about-0.6gallon per square foot of disengaging surface per hour,Substantiallyglower evaporation rates may be used elfectively,Satisfactory results have been i d u n ev p a ion. rate a u as gallonPatented Nov. 28, 1961 of methanol per square foot of disengagingsurface per hour. Rates below about 0.4 gallon do not appear to haveadded advantage and are'usually not recommended because of excessiveprocessing time and cost. Evaporation rates substantially in excess of0.6 gallon per square foot of surface per hour, for instance evaporationrate of 0.8. gallon, have been found to result in an inferior grease.Usually a methanol evaporation rate within the range of about 0.5 toabout 0.6 gallon per square foot of surface per hour is preferred.

After the methanol has been substantially completely expelled, the batchis heated to at least 300 F., with stirring, until substantially all thewater present therein has been driven 01f.

A third essential feature of my present process is the character of thefatty acid used. For this fatty constitucut, I use a straight-chain,saturated, unsubstituted fatty acid consisting predominantly of a fattyacid or a mixture of fatty acids containing 20 to 22 carbon atoms permolecule, i.e., arachidic or behenic acid or a mixture thereof. The useof unsaturated or substituted fatty acids, and even straight-chain,saturated, unsubstituted fatty acids of lower molecular weight, has notresulted in greases having the desired properties. A mixture of aboutequal proportions of arachidic and behenic acids is recommended. Behenicacid alone produces excellent results, but its cost is presently toogreat to be economically attractive. V

I have, with particular advantage, used a mixture of fatty acidsmarketed by Arch-er-DanielsMidland Company under their proprietary tradename Hydrofol Acid AB? and having the following analysis and approximatecomposition:

TABLE 1 of the fatty acid. However, most advantageous results have beenobtained where the said molar ratio was about Other conditions remainingconstant, I have found that the maximum yield, i.e., the maximumconsistency of the finished grease for a given amount of thickener, willvary somewhat with the temperature to which the batch is heated in thefinal stage of the operation. Maximum yields have usually been obtainedwhere the final temperature is about 450 F. However, most desirableperformance of the greaseunder the A.S.T.M. wheel hearing performancetest has been obtained byusing a finish ingtemperature of about 350 F. i

For most advantageous results, particularly with respect to oil leakageunder conditions of the A.S.T.M. wheel bearing performance test, I havefound it necessary to incorporate in the grease a minor proportion of adispersing agent or stabilizer, such as a high molecular weight sulfonicacid, more particularly a sulfonic acid of a molecular weight of about400 to about 500.

The optimum propotrion of such sulfonic to be used will vary somewhatdepending upon the particular suli fonic acid used, the proportions andidentity of the other ingredients and also the desired characteristicsof the re- Titer (3.. 60-63 Iodine value max 5 Acid value 178-185Saponificat-ion value 179-186 Color Lovibond, 5 A" max 25Y/2.5RCalculated molecular weight 302-314 Spec. grav., 100/25 C. 0.828Approximate composition, percent:

V14 2 C 13 C13 7 V C 30 C22 The nature of the petroleum lubricating oilfraction used is subject to'considerable variation depending upon theintended use of the grease and the specificcharacusing the previouslydescribed Hydrofol Acid AB and a'naphthenic oil fraction havingaviscosity of about seconds SSU at 210 F., I have, with particular advantage, used approximately one part, by weight, of the sultant grease.When used, the stabilizer should be incorporated in the mixture of thefatty acid, petroleum oil and colloidal barium carbonate suspensionprior to the evaporation of the methanol therefrom.

I have, with particular advantage, used for this purpose a solution of39% dinonylnaphthalene sulfonic acid in naphtha, and have found it topromote better dispersion of the soap and colloidal carbonate in the oiland to improve the lubricating characteristics and stability of theresultant grease under operating conditions.

. As previously indicated, the proportion of the sulfonic acid used doesnot appear to be particularly critical. However, for most satisfactoryresults, I have used approximately one part of the above-describedsulfonic acid, dry weight basis, for each 10 parts of the Hydrofol AcidAB. Where the stabilizer is used as above described, I have, withadvantage, increased the finishing temperature of the batch to about 450-F., thus obtaining maximum yield with a minimum of oil leakage underconditions of the A.S.T.M. wheel bearing performance test.

' The invention and the utility thereof will be further illustrated bythe following specific examples in which the variables have beenreduced, so far as practical, for comparative purposes. It will beunderstood, however, that the invention is not restricted to thespecific material and operating conditions of these illustrativeexamples.

Example I ing 12.5% barium and produced as previously described herein.These materials were mixed in the following acid for each 5 or 6 partsof the on; Where a less viscous oil is used, a somewhat largerproportion of fatty 1 acid will be required to produce a grease ofeqfialcon- 1 sistency' or dropping point, other conditions remainingconstant, i 2' Also using the materialsjustv named, I have, with advantage, varied the proportion of barium carbonate used over a rangeequivalent to2 to5 mols of-barium per mol proportions by weight:

' Parts Fatty acid V 50 Oil fraction i 336 Colloidal suspension 352Themixture was mildly heated to atemperature within and ten minutes,during which timejthe methyl alcohol mixture.

the range'of F. to 200 F. for a period of one hour s The temperatur'e ofthe batch was then raised to approximately 300 F., while stirring, andmaintained at that temperature for about 20 minutes with continuedstirring. The temperature was then increased to approximately 350 F.,with continued stirring, and maintained at that temperature for anadditional to 30 minutes. The heating and stirring were thendiscontinued and the batch permitted to cool to room temperature. Theresultant grease was of a somewhat crumbly nature but upon millingresulted in a smooth, homogeneous grease having the properties set forthin the subsequent tabulation, Table 2.

Example II In this operation, the fatty acid, the oil and the colloidalsuspension of barium carbonate were the same, and were used in the sameproportions, as in the preceding example. Unlike Example I, there wasincorporated in the mixture, prior to evaporating the methanoltherefrom, 13 parts by weight of a 39% dinonylnaphthalene sulfonic acid,of a molecular weight of about 425, in naphtha, as a stabilizing ordispersing agent.

This mixture was preliminarily mildly heated, as described in Example I,for evaporating the methanol and the heating was thereafter continuedwith stirring at a temperature of 300 F. for approximately minutes. Withcontinued stirring the temperature of the batch was then raised to about450 F. and maintained at that temperature for approximately 15 minutes.The stirring and heating were then discontinued and the batch permittedto cool to room temperature. The batch was then milled which resulted ina smooth homogeneous grease having the properties set forth insubsequent Table 2.

Example 111 In this operation, the fatty acid, the oil and the colloidalsuspension of barium carbonate, and the proportion thereof, wereidentical with those used in Example I and the procedure wassubstantially identical therewith except that the maximum finaltemperature of the batch was approximately 300 F. A serviceable greaseresulted. However, under final test, the product was somewhat inferiorto that of Example I or Example II, as will appear from the followingtabulation:

TABLE 2 Ex. I Ex. II Ex. III

A.S.T.M. Dropping Point, F 301 383 300+ Scale Penetration (unworked) 132110 181 Equivment A.S.T.M. Penetration 263 225 348 Rolling StabilityTest (2 hrs., dry,

Room Temp):

Original Penetration 84 70 136 Final Penetration 102 98 183 WheelBearing Performance Test (6 hrs,

220 F., 90 gram pack): Oil Leakage grams 7 2 0.5 10 1 Four-Ball WearTest, Wear Scar Diameter, mm.:

6 kg. Load, 130 F., 1,800 r.p.m 40 kg. Load, 300 F., 600 r.p.m Four-BallWeld Test 200 kgs frared analysis any indication of the presence of acomplex of the excess barium carbonate with the barium soap.

The herein referred to A.S.T.M. dropping point values and A.S.T.M. wheelbearing performance test, were at; termined and carried out inaccordance with the pre with the procedure described in the articlebeginning on page 1 of National Lubricating Grease Institute Spokesman,vol. VI, No. 12, of March 1943.

I claim:

1. Process for producing lubricating greases comprising the followingsteps, mixing a petroleum lubricating oil fraction, a fatty acidconsisting predominantly of straightchain, saturated, unsubstitutedfatty acids containing from- 20 to 22 carbon atoms per molecule and acolloidal suspension of barium carbonate in methanol, the latter in aproportion within the range equivalent to about 2 to about 5 mols ofbarium carbonate per mol of fatty acid and produced by reacting withanhydrous methyl alcohol, to form a clear solution, an amount of bariumoxide equivalent to about 10% to about 15% barium, based on the weightof the alcohol, and adding to the resultant solution and thoroughlydispersing therein, with stirring to form a homogeneous solution, anamount of water within the range from about 1 mol to about 4 mols permolof barium present in the solution, thereafter dissolving carbon dioxidein the resultant solution in a molar proportion at least equal to themols of barium present therein and heating the resultant mixture withrefluxing until a substantially clear colloidal solution is obtained,

mildly heating the mixture of oil, fatty acid and colloidal carbonatesuspension to a temperature and at a rate adapted to expel the methanoltherefrom at a rate not exceeding about 0.6 gallon of methanol persquare foot of disengaging surface per hour until the methanol has beensubstantially completely evaporated therefrom, increasing thetemperature of the mixture to at least 300 F. but not exceeding about450 F. and continuing the heating, with stirring, until substantiallyall the water present therein has been driven off, then graduallycooling the mixture to room temperature and milling the resultant cooledmixture to a smooth grease.

2. The process of claim 1 in which the barium carbonate suspension usedis one containing 12.5% barium and is used in a proportion equivalent to3.5 mols of barium per mol of fatty acid.

3. The process of claim 1 in which the colloidal suspension of bariumcarbonate used is one produced by reacting with the anhydrous methylalcohol an amount of barium oxide equivalent to about 12.5% barium,adding to the resultant solution and thoroughly dispersing therein, withstirring to form a homogeneous solution, about 2 mols of water, per molof barium present in the solution, and thereafter saturating theresultant solution with carbon dioxide.

4. The process of claim 1 in which the grease batch is finally heated toa temperature within the range of 350 F. to 450 F.

5. The process of claim 1 in which the petroleum lubricating oilfraction is a solvent refined naphthenic fraction having a viscosity of50 SSU at 210 F.

6. The process of claim 1 inwhich a sulfonic acid dispersing agent,having a molecular weight within the range of about 400 to about 500,and in a minor proportion efiectiveto promote dispersion of thecolloidal carbonate and soap in the mineral oil, is incorporated in themixture of oil, fatty acid and colloidal carbonate suspension prior toexpelling the methanol therefrom.

7. The process of claim 1 in which about 10% of dinonylnaphthalenesulfonic acid, based on the weight of the fatty acid used, isincorporated in the mixture of predominantly of straight-chain,saturated, unsubstituted,

fatty acid containing from 20-22 carbon atoms per molecule,dinonylnaphthalene sulfonic acid and a colloidal suspension of bariumcarbonate in methanol, the suspension having'been produced by reactingwith anhydrous methyl alcohol, to form a clear solution, an amount ofbarium oxide equivalent to about 12.5% barium, adding to the resultantsolution and thoroughly dispersing therein, with stirring to form ahomogeneous solution, about 2 mols of water, per mol of barium presentin the solution, and thereafter saturating the solution ,with carbondioxide and heating the resultant mixture with refluxing until asubstantially clear colloidal solution is obtained, mildly heating themixture of oil, fatty acid, carbonate suspension and sulfonic acid to atemperature within a range of 170200 F. until the methanol'has beensubstantially completely expelled therefrom, then heating the batch toabout 300 F., with stirring, until the water present in the batch hasbeen substantially completely eliminated, then increasing thetemperature of the batch to about 450 F., with continued stirring,thereafter cooling the batch to room temperature and milling theresultant grease to a smooth homogeneous consistency, the proportions ofthe respective ingredients used being approximately as follows: 7

Parts by weight 50 Fatty arid Oil 336 Carbonate suspension 352 Sulfonicacid 9. A stable, substantially anhydrous homogeneous lubricating greasehaving reserve alkalinity and consisting essentially of a petroleumlubricating oil fraction thickenedto the desired consistency with anadmixture of 'a barium soap of a straight-chain, saturated,unsubstituted,

fatty acid consisting predominantly of fatty acidscontaining from 20 to22 carbon atoms per molecule, and colloidal barium carbonate, theproportion of soap, expressed inlterms of the fatty acid content, beingabout 1 part of fatty acid for each 5-6 parts of oil and the molarproportion of colloidal barium carbonate present in the grease beingabout 1 to about 4 times the weight of that combined with the fattyacid, said grease having an A.S.T.M. dropping point of at least 300 F.,and which under the, A.S.T.M. wheel bearing performance test, 6 hours at220 F., gram pack, suffers an oil leakage not exceeding about 10 grams.7

10. A stable,'substantially anhydrous homogeneous lubricating greasehaving reserve alkalinity and consisting essentially of a solventrefined naphthenic petroleum oil fraction thickened to the desiredconsistency with an admixture of a barium soap of a straight-chain,saturated, unsubstituted fatty acid consisting predominantly of fattyacids containing from 20 to 22 carbon atoms per molecule, colloidalbarium carbonate and a sulfonic acid dispersing agent having a molecularweight of 400-500, the proportion of soap, expressed in terms of thefatty acid content, being about 1 part of fatty acid for each 5-6 partsof oil and the molar proportion of colloidal barium carbonate present inthe grease being about 1 to about 4 times the weight of that combinedwith the fatty acid, said grease having an A.S.T.M. dropping point inexcess'of 350 F. and which under the A.S.T.M. wheel bearing performancetest, 6 hours at 220 F., 90 gram pack, suffers an O1]. leakage of lessthan 5 grams.

References Cited in the file of this patent UNITED STATES PATENTS2,154,383 Ott et a1. Apr. 11, 1939 2,417,433 McLennan Mar. 18, 19472,503,749 Langer et a1 Apr. 11, 1950 2,629,692 Liehe Feb. 24, 19532,865,956 Ellis et a1. Dec. 23, 1958 2,889,279 Carlyle et al June 2,1959 FOREIGN PATENTS 507,259 Canada Nov. 9, 1954 507,437 Canada Nov. 16,1954

1. PROCESS FOR PRODUCING LUBRICATING GREASE COMPRISING THE FOLLOWINGSTEPS, MIXING A PETROLEUM LUBRICATING OIL FRACTION, A FATTY ACIDCONSISTING PREDOMINANTLY OF STRAIGHTCHAIN, SATURATED, UNSUBSTITUTEDFATTY ACIDS CONTAINING FROM 20 TO 22 CARBON ATOMS PER MOLECULE AND ACOLLOIDAL SUSPENSION OF BARIUM CARBONATE IN METHANOL, THE LATTER IN APROPORTION WITHIN THE RANGE EQUIVALENT TO ABOUT 2 TO ABOUT 5 MOLS OFBARIUM CARBONATE PER MOL OF FATTY ACID AND PRODUCED BY REACTING WITHANHYDROUS METHYL ALCOHOL, TO FORM A CLEAR SOLUTION, AN AMOUNT OF BARIUMOXIDE EQUIVALENT TO ABOUT 10% TO ABOUT 15% BARIUM, BASED ON THE WEIGHTOF THE ALCOHOL, AND ADDING TO THE RESULTANT SOLUTION AND THOROUGHLYDISPERSING THEREIN, WITH STIRRING TO FORM A HOMOGENEOUS SOLUTION, ANAMOUNT OF WATER WITHIN THE RANGE FROM ABOUT 1 MOL TO ABOUT 4 MOLS PERMOL OF BARIUM PRESENT IN THE SOLUTION, THEREAFTER DISSOLVING CARBONDIOXIDE IN THE RESULTANT SOLUTION IN A MOLAR PROPORTION AT LEAST EQUALTO THE MOLS OF BARIUM PRESENT THEREIN AND HEATING THE RESULTANT MIXTUREWITH REFLUXING UNTIL A SUBSTANTIALLY CLEAR COLLOIDAL SOLUTION ISOBTAINED, MILDLY HEATING THE MIXTURE OF OIL, FATTY ACID AND COLLOIDALCARBONATE SUSPENSION TO A TEMPERATURE AND AT A RATE ADAPTED TO EXPEL THEMETHANOL THEREFROM AT A RATE NOT EXCEEDING ABOUT 0.6 GALLON OF METHANOLPER SQUARE FOOT OF DISENGAGING SURFACE PER HOUR UNTIL THE METHANOL HASBEEN SUBSTANTIALLY COMPLETELY EVAPORATED THEREFROM, INCREASING THETEMPERATURE OF THE MIXTURE TO AT LEAST 300* F. BUT NOT EXCEEDING ABOUT450*F. AND CONTINUING THE HEATING, WITH STIRRING, UNTIL SUBSTANTIALLYALL THE WATER PRESENT THEREIN HAS BEEN DRIVEN OFF, THEN GRADUALLYCOOLING THE MIXTURE TO ROOM TEMPERATURE AND MILLING THE RESULTANT COOLEDMIXTURE TO A SMOOTH GREASE.